Exterior shell of a highway tractor



FIG. 1 is a right, front perspective view of an exterior shell of ahighway tractor showing our new design, it being understood that thebroken lines are for illustrative purposes only and form no part of theclaimed design;

FIG. 2 is a right side elevation view thereof, the left side being amirror image of that shown; and

FIG. 3 is a front elevation view thereof.

The ornamental design for an exterior shell of a highway tractor, asshown and described.